Image reading apparatuses included in copiers, scanners, and multifunction apparatuses having a copy function and a scanning function, contain auto document feeders (“ADF”) to feed documents from an input tray through a feed path to an output tray. In addition, in order to read a document printed on a first surface and a second surface, known document feeders that feed a document for double-sided reading by reversing the document's leading end trailing.
FIG. 14 shows a feed path in a conventional document feeder capable of double-sided reading. As shown in the figure, a document P is placed on an input tray 90 with a first surface (a first page) facing upward. This document P is fed to a feed path 92 by a pickup roller 91. In the feed path 92, the document P is fed by feed rollers 93 provided as appropriate, and the first surface of the document P is read by an image reading device, such as CCD or CIS, when the document P passes a reading position X. When a sensor detects a trailing end of the document P, of which the first surface has been read, ejection rollers 94 are stopped with the trailing end of the document P nipped. As the ejection rollers 94 are rotated backward, the document P is fed to a switchback path 95. The document P goes from the switchback path 95 toward an upstream side of the reading position X of the feed path 92. As a result, the leading end and the trailing end of the document P are reversed, and the document P is inverted.
Then, the document P is fed by the feed rollers 93, and the second surface of the document P is read by the image reading device when the document P passes the reading position X. When a sensor detects the trailing end of the document P, of which the second surface now has been read, the ejection rollers 94 are stopped again with the trailing end of the document P nipped, and then the document P is fed back to the switchback path 95. When the document P enters the feed path 92 again from the switchback path 95, its leading end and trailing end are reversed again, that is, the first surface faces the reading position X, and the document P is again inverted. The document P then is fed on the feed path 92 and ejected to an output tray 96 with its first surface facing downward. Thus, the first and second surfaces of the document P are read, and the document P is ejected to the output tray 96 in the same sequence as the original documents P, in the original order, placed on the input tray 90.
In the feed paths shown in FIG. 14, the feed path 92 and the switchback path 95 are arranged vertically above the reading position X requiring additional space above the reading position X thus increasing the size of the apparatus. In addition, a part of a document P being fed back may trail down onto the output tray 96, resulting in mixing up of the order of the stack of documents P already scanned and ejected onto the output tray 96.
In the feed paths of the document feeder shown in FIG. 14, guide members for guiding the document P to a specified feed path are disposed in a position where the switchback path 95 branches from the feed path 92, and a position where the switchback path 95 connects to the feed path 92. The guide members may be guide flaps capable of changing a path to the feed path 92 or a path where the feed path 92 and the switchback path 95 continue. The guide flaps are generally operated by a drive device such as a solenoid. Generally, the greater the number of guide members, the greater the number of drive devices is required, as well as additional space for the guide members and drive devices, and controls for each drive device.